A team of researchers from the University of Minnesota Centre for Biorefininghave joined forces with the St Paul Minnesota Metropolitan Council for growing algae in the wastewater treatment plant.
The algae is designed to remove nitrogen and phosphorous from the water befor it becomes flushed into the Mississippi River and the Gulf of Mexico.
The algae can also be used to produce biofuels and the nitrogen and phosphorous used for fertiliser.
A report in Biomass Magazine says that lengthy research and experimenting went into choosing the algae strains, and the discovery that centrate is the optimal element.
The project will eventually save Met Council the cost of removing phosphorus to meet Minnesota Pollution Control Agency mandates, which is usually done by adding salts to the water.
Using an enclosed photobioreactor allows algae growth to occur in a smaller area. It is maintenance-free and allows growth throughout the tank, instead of just on the surface.
The team hopes to use gaseous waste from the Met Council’s fluidized bed gasifier in the future, but currently gets its carbon dioxide supply from a pure tank. The team also is in early discussions with Xcel Energy to obtain waste carbon dioxide and maybe nitrogen oxide, according to Biomass Magazine.